French patent application FR 2,431,371 discloses a printing unit cylinder with an axially extending groove to allow for the mounting of printing plates or conventional blankets on its circumference. Because of the groove, the printing unit cylinder is imbalanced during its rotation around its axially extending central axis. The consequences of the imbalanced state of the printing unit cylinder are sought to be cured by a liquid filling an inner chamber of the printing unit cylinder.
The solution of FR 2,431,371 does not allow for an additional gas chamber to change a cylinder blanket or plate on the circumference of the printing unit cylinder. Furthermore, an evenly distributed temperature profile cannot be achieved, since the circumference of the cylinder is interrupted by an axially extending groove where plate or blanket edge clamping elements are located. Since there is a gap extending on the circumference of this cylinder, the heat generation is not evenly distributed. An uneven heat input will cause an uneven temperature distribution.
European patent specification EP 0 421 145 B1 discloses a printing machine for printing on material in sheet or web form. A gapless, tubular sleeve can be removed by radially expanding the tubular sleeve. Gas chambers are provided for the sole purpose of allowing pressurized gas to blow off the tubular gapless sleeve from the circumference of the respective printing unit cylinder. No mechanism is provided to reduce an unevenly distributed temperature profile around the print unit cylinders in the circumferential direction.
U.S. Pat. No. 4,183,298 discloses a water cooled ink roller for printing presses. Within the hollow roller body there is provided a cylindrical partition having a conical shape. Due to the conical shape of the cylindrical partition and the uneven mass distribution within the ink roller, a non-uniform heat distribution may occur.
U.S. Pat. No. 4,534,289 discloses a cooling roller with different preselected cooling zones. To keep the ink temperature largely constant during operating interruptions a displacement body is disposed in the interior of the ink roller.
On printing unit cylinders having a small cylinder diameter to cylinder length ratio, an uneven temperature distribution on the printing unit cylinders circumference may effect a bending of the cylinder. Uneven temperature distribution on the printing unit cylinders circumference can be further amplified by high nip passing frequencies encountered at high press speeds. The smaller the cylinder diameter compared to its axial length, the more the printing unit cylinder tends to bend perpendicular to its axial extension. The absolute temperature level, furthermore, is of less importance than an even temperature profile around the printing unit cylinder circumference.